UP to 55,000 smear samples might need to be re-tested after a number of women were wrongly given the all-clear, it has emerged reports the BBC.
As first revealed by GP magazine Pulse, 17 women in Essex were wrongly told their results were normal.
They had been tested at a lab run jointly by Southend, Basildon and Thurrock Hospitals, and a private firm.
Public Health England has told the BBC tens of thousands of samples may have to be reviewed.
Women are unlikely to know if their samples are being re-tested unless they get called for further tests.
Basildon and Thurrock NHS Trust says 900 test results had been reviewed so far.
The first stage of re-testing, the trust said, will involve 2,500 re-tests.
That testing is expected to be completed within the next two weeks, a hospital trust spokeswoman said.
If the results of that re-testing vary significantly from what would be expected, the spokeswoman said, then re-testing could be expanded to all 55,000 women who had smear tests during the past two years.
“We understand that this is a potentially worrying time for the women involved and would like to reassure all women covered by the locally provided cervical screening programme that this was an isolated incident,” the trust said in a statement.